1. Field of the Invention
The present invention relates generally to ceiling fans and, more particularly, to a system for suspending a ceiling fan.
2. Related Art
Ceiling fans have become an increasingly popular supplementary means of conditioning air within both commercial and residential buildings. Notwithstanding the widespread use of ceiling fans, one continuing problem which faces ceiling fan designers is the tendency of ceiling fans to "wobble", or pivot about the point of suspension. Ceiling fan wobble may exist regardless of the type of conventional system used to mount the ceiling fan, due to fan blade imbalance, which may result from a variety of discrepancies associated with the ceiling fan blades including variations in blade pitch angle, dihedral angle, uneven circumferential spacing between adjacent blade pairs, blade warpage and uneven radial spacing of the blades from the vertical axis of rotation. However, ceiling fan wobble is more prevalent in ceiling fans suspended from a ceiling by a canopy and downrod arrangement, as subsequently discussed in greater detail. Ceiling fan wobble and the associated vibration creates undesirable noise, is visually distracting and may adversely affect the service life of the ceiling fan.
The fan blades of ceiling fans must be positioned at a certain optimum distance from the floor to achieve proper air circulation within the room in which they are installed. This may be accomplished in rooms having relatively high or vaulted ceilings by suspending the fan from the ceiling with a system which includes a canopy and downrod/ball assembly. While conventional systems of this type have enjoyed widespread use, they have a tendency to exacerbate the fan wobble problem as subsequently discussed in conjunction with FIGS. 1-7.
FIG. 1 is a fragmentary elevation view, partially in cross-section, illustrating a portion of a ceiling fan 10 and a conventional system 12 for suspending fan 10 from a ceiling (not shown). Ceiling fan 10 includes a motor (not shown) and a plurality of fan blades (not shown) connected to a rotatable portion of the motor, typically by blade irons (not shown). Ceiling fan 10 further includes a motor housing 14, which may have a unique configuration or decorative outer surface. The ceiling fan 10 typically includes a switch housing suspended below the motor housing 14 and may optionally include a light fixture. A stationary portion of the motor, such as the stator shaft (not shown) may be connected to the motor housing via an adapter 16, with the upper portion of adapter 16 being shown in FIG. 1. Adapter 16 is connected to the suspension system 12, for supporting the ceiling fan 10.
The suspension system 12 includes a hollow canopy 18 having an upper end portion 20 which is effective for mounting the ceiling fan directly to the ceiling or to an electrical junction box disposed above the ceiling. With regard to canopy 18, the upper end portion comprises an annular flange which may be attached to the ceiling or junction box via brackets (not shown). The suspension system 12 further includes a downrod 22 having a lower end which is attached to the adapter 16, typically by threading the lower end of the downrod 22 into adapter 16. The suspension system 12 further includes a ball 24 disposed in surrounding relationship with an upper end of the downrod 22 and connected thereto by a fastener, such as a set screw (not shown) extending radially through an annular wall of ball 24 into engagement with the downrod 22.
Canopy 18 defines an interior space 28 and includes a seat 30 extending upwardly from a lower end 32 of canopy 18 and defining an aperture 34 formed in the lower end 32. Seat 30 is discontinuous in a circumferential direction as subsequently explained further. The ball 24 is disposed partially within the interior space 28 defined by canopy 18, with a spherical outer surface 26 of ball 24 engaging an arcuate inner surface of the seat 30. As shown in FIG. 1, a portion of ball 24 extends through the aperture 34 and protrudes below the lower end 32 of canopy 18. The suspension system 12 further includes a pin 36 which extends through apertures 37 formed in the upper end of the downrod 22 and includes opposing ends 38, 40 which are disposed in longitudinally extending slots 42 formed in the ball 24. This permits the vertical suspension loads of the ceiling fan 10 to be reacted through the downrod 22, pin 36 and ball 24 to the canopy 18.
The spherical outer surface 26 of the ball 24 and the arcuate inner surface of the seat 30 of canopy 18 permits the ball 24 to pivot within seat 30 of canopy 32. Accordingly, the ceiling fan may pivot about the center of rotation of ball 24, corresponding to the center (indicated at G in FIGS. 3, 4, 5 and 7) of the spherical radius defining the outer surface of the ball 24. The foregoing pivoting of ball 24 and resultant pivoting of the ceiling fan 10, is necessary for the following reasons. In the first instance, ball 24 must be free to pivot when ceiling fan 10 is mounted to a vaulted, or sloped ceiling. In this instance, the design intent is that a longitudinal centerline axis 54 of the ceiling fan 10 remains substantially vertically disposed. Another reason for requiring the ball 24 to pivot within seat 30 of canopy 32, is to accommodate wobble of ceiling fan 10 due to an imbalance of the fan blades or rotating portion of the motor. Rigidly mounting the ceiling fan 10 to the ceiling (i.e., eliminating the pivoting motion of ball 24 within seat 30) would result in damage to the ceiling as a result of the ceiling fan wobble which typically occurs.
The canopy 18 further includes a radially extending tab 50 which engages a longitudinally extending slot 52 formed in the outer surface 26 of the ball 24. The tab 50 is located circumferentially at a position where the seat 30 of canopy 18 is discontinuous. Furthermore, as shown in FIG. 2, the tab 50 extends radially outward from the bottom end 32 of canopy 18. It is important to note that when the ceiling fan is at rest, with the ball 24 engaged in seat 30 of canopy 18 as shown in FIG. 1, the tab 50 of canopy 18 engages the slot 52 of ball 24 at a position which is below the center G of the spherical radius defining the outer surface of the ball 24. This causes the ball 24 to pivot about an axis which does not pass through the center G as subsequently discussed.
The engagement of the tab 50 in slot 52 of ball 24 reacts the rotational torque created by the motor of the ceiling fan 10 and prevents the ball 24 from rotating within seat 30 about a longitudinal centerline axis 54 of the fan 10. Accordingly, the ceiling fan 10 is prevented from rotating about the longitudinal centerline axis 54 of the ceiling fan 10. This prevents the electrical wires (not shown) which pass upward through the hollow interior of the downrod 22 to the junction box, from becoming entangled. However, the local pinning of the ball 24, via tab 50 in slot 52, causes the ball 24 to pivot within seat 30, in reaction to the motor torque, so that the centerline axis 54 is canted relative to vertical, during operation of the ceiling fan 10. Furthermore, the inventor has determined that as the ball 24 pivots within seat 30 of canopy 18 an undesirable rotation (less than one revolution) of the ball 24 and downrod 22 occurs in reaction to the motor torque. This motion is superimposed on the generally circular motion created by imbalances in the fan blades or other rotating components, which normally occurs. The partial rotation of the ball 24 and downrod 22, in reaction to the motor torque, exacerbates the ceiling fan wobble problem as further discussed in conjunction with FIGS. 3-7. Furthermore, it is believed that the partial rotation of the ball 24 and downrod 22 in reaction to the motor torque, creates a magnified, elliptical wobble pattern, which has been observed with ceiling fans having the type of suspension system discussed previously, rather than a circular fan wobble pattern.
When the ceiling fan 10 is energized, a rotational torque is applied to the ball 24 through the downrod 22. This rotational torque tends to rotate the ball 24 within seat 30 of canopy 32 about the center G of the spherical radius defining the outer surface of ball 24. However, since the ball is pinned at one location, by the engagement of tab 50 in slot 52, a secondary pivot point is established. As a result, the ball 24 pivots about an axis EF (shown in FIGS. 3,5 and 7) which passes through the center G of the spherical radius of the ball 24 and the location, indicated generally at H, where the tab 50 engages slot 52. This causes the centerline axis 54 of the ceiling fan 10 (which passes through the center of the downrod 22) to be canted, or disposed at an angle relative to vertical, during operation of the ceiling fan 10.
FIGS. 3-7 are provided in an attempt to further illustrate the complex motion of the ball 24, within the canopy seat 30, and the downrod 22 attached to the ball 24. As shown in FIG. 3, axis EF is oriented at an acute angle 56 relative to a horizontal axis 58 passing through the center G of the spherical radius defining the outer surface of ball 24. Axis EF is not perpendicular to the centerline axis 54 of the fan 10, but instead is disposed at an acute angle 60 from axis 54. Furthermore, the axis EF remains stationary as the ball 24 and downrod 22 move. Accordingly, the angle between axis EF and centerline 54 changes as the ball 24 and downrod 22 move. The inventor has determined that this orientation of axis EF relative to the centerline axis 54 of fan 10 is the reason that fan 10 becomes canted relative to vertical during operation.
A plane ABCD is illustrated in FIGS. 4-7 which passes longitudinally through the center of downrod 22 and intersects the axis EF passing between points G and H. In FIG. 6, plane ABCD is substantially vertically disposed and intersects an outer surface of the downrod 22 at points I and J which are horizontally aligned with one another. Ball 24 and downrod 22 may describe a first motion within plane ABCD as shown by direction arrow 56 in FIG. 4. Also, as discussed previously, the ball 24 and downrod 22 may pivot about the axis EF. When the ball 24 and downrod 22 are pivoted about axis EF to the position shown in FIGS. 4 and 5 points I and J on downrod 22 are displaced horizontally from one another by a distance X, as shown in FIG. 5. This displacement of points I and J is equivalent to that which would occur if the downrod 22 were rotated counterclockwise, as viewed from a position below fan 10, about the longitudinal centerline axis 54 of fan 10. When the ball 24 and downrod 22 are moved to the position shown in FIG. 7, it may be seen that points I and J on downrod 22 are displaced by a horizontal distance Y, which is equivalent to that which would occur if the downrod 22 were rotated in a clockwise direction, as viewed from a position below fan 10, about the longitudinal centerline axis 54 of the ceiling fan 10. The inventor has deduced that conversely, an attempt to rotate the downrod 22 and ball 24 about the longitudinal centerline axis 54 of fan 10, such as that caused by the application of the rotational torque of the motor of fan 10, causes the downrod 22 and ball 24 to pivot about axis EF such that the longitudinal axis 54 is canted or angled relative to vertical during the operation of fan 10. The inventor has observed that with conventional ceiling fans employing a suspension system such as that described with respect to FIGS. 1-7, the centerline of the ceiling fan, such as centerline 54, is in fact angled relative to vertical during operation of the fan resulting in an undesirable appearance. Furthermore, the circular motion created by any imbalance in the rotating parts of the ceiling fan, such as the fan blades, adds to and subtracts from the motion created by the torque of the ceiling fan motor such that the ceiling fan jerks during operation and describes an elliptical fan wobble pattern. The inventor has further determined that the magnitude of the angle that the centerline of the ceiling fan is displaced relative to vertical, increases as the motor torque increases. Since the current trend is to provide ceiling fans with increased motor torque, so as to produce an increase in the amount of air circulated by the fan, as measured in cfm, the foregoing problems associated with conventional ceiling fan suspension systems, represents an ever-increasing problem for ceiling fan designers.
Another problem associated with the use of conventional ceiling fan suspension systems of the type illustrated in FIGS. 1-7, is related to the use of the set screw, discussed previously, to attach the pivoting ball 24 to the downrod 22. The set screw tends to cause the downrod 22 to be off center relative to ball 24 somewhat, resulting in the centerline 54 of fan 10 to be canted related to vertical. Furthermore, if the set screw is improperly assembled, such that the downrod 22 is free to pivot somewhat relative to the ball 24, the ceiling fan wobble problem is exacerbated.
In view of the foregoing deficiencies with known systems for suspending ceiling fans, there remains a need for an improved system which alleviates ceiling fan wobble.